# Troubleshooting network issues
<a name="network-issues"></a>

If you are experiencing network issues, you can use the procedures shown here to diagnose the problem.

## You want to capture a packet trace
<a name="capture-packet-trace"></a>

Packet tracing is the process of verifying the path of a packet through the layers to its destination. You control the packet tracing process with the following NetApp ONTAP CLI commands:
+ **network tcpdump start** – Starts packet tracing
+ **network tcpdump show** – Shows currently running packet traces
+ **network tcpdump stop** – Stops a running packet trace

These commands are available to users who have the `fsxadmin` role on your file system.

**To capture a packet trace from your file system**

1. To SSH into the NetApp ONTAP CLI of your file system, follow the steps documented in the [Using the NetApp ONTAP CLI](managing-resources-ontap-apps.md#netapp-ontap-cli) section of the *Amazon FSx for NetApp ONTAP User Guide*.

   ```
   ssh fsxadmin@file-system-management-endpoint-ip-address
   ```

1. Enter the diagnostic privilege level in the ONTAP CLI by using the following command.

   ```
   ::> set diag
   ```

   When prompted to continue, enter `y`.

   ```
   Warning: These diagnostic commands are for use by NetApp personnel only.
   Do you want to continue? {y|n}: y
   ```

1. Identify the location on your file system where you want to save your packet trace. The volume must be online and must be mounted in the namespace with a valid junction path. Use the following command to check for volumes that fulfill those criteria:

   ```
   ::*> volume show -junction-path !- -fields junction-path
   vserver volume    junction-path 
   ------- --------- ------------- 
   fsx     test_vol1 /test_vol1    
   fsx     test_vol2 /test_vol2
   fsx     test_vol2 /test_vol3
   ```

1. Start the trace with the minimum required arguments. Replace the following:
   + Replace *node\$1name* with the name of the node (for example, `FsxId01234567890abcdef-01`).
   + Replace *svm\$1name* with the name of your storage virtual machine (for example, `fsx`).
   + Replace *junction\$1path\$1name* with the name of the volume (for example, `test-vol1`).

   ```
   ::*> debug network tcpdump start -node node_name -ipspace Default -pass-through "-i e0e -w /clus/svm_name/junction_path_name"
   Info: Started network trace on interface "e0e"
   Warning: Snapshots should be disabled on the tcpdump destination volume while packet traces are occurring. Use the
   "volume modify -snapshot-policy none -vserver fsx -volume test_vol1" command to disable Snapshots on the
   tcpdump destination volume.
   ```
**Important**  
Packet traces can only be captured on the `e0e` interface and in the `Default` IP space. In FSx for ONTAP, all network traffic uses the `e0e` interface.

   When using packet tracing, keep the following in mind:
   + When starting a packet trace, you must include the path to where you want to store the trace files, in this format: /clus/*svm\$1name*/*junction-path-name*
   + Optionally, provide the file name for the packet trace. If the filter\$1name is not specified, it is automatically generated in the form: *node-name*\$1*port-name*\$1*yyyymmdd\$1hhmmss*.trc 
   + If rolling traces are specified, the filter\$1name is suffixed with a number that indicates the position in the rotation sequence.
   + The ONTAP CLI also accepts the following optional **-pass-through** arguments:

     ```
     -B, --buffer-size=<KiB>
     -c <number_of_packets>
     -C <file_size-mB>
     -F <filter_expression_filename>
     -G <rotate_seconds>
     --time-stamp-precision {micro|nano}
     -Q, --direction {in|out|inout}
     -s, --snapshot-length=<bytes>
     -U, --packet-buffered
     -W <rotate_file_count>
     <filter-expression>
     ```
   + For information about filter expressions, see [pcap-filter(7) man page](https://www.tcpdump.org/manpages/pcap-filter.7.html).

1. View the traces in progress:

   ```
   ::*> debug network tcpdump show
   Node                     IPspace  Port     Filename
   -----------------------  -------- -------- --------
   FsxId123456789abcdef-01  Default  e0e      /clus/fsx/test_vol1/FsxId123456789abcdef-01_e0e_20230605_181451.trc
   ```

1. Stop the trace:

   ```
   ::*> debug network tcpdump stop -node FsxId123456789abcdef-01 -ipspace Default -port e0e
   Info: Stopped network trace on interface "e0e"
   ```

1. Return to the admin privilege level:

   ```
   ::*> set -priv admin
   ::>
   ```

1. Access the packet traces.

   Your packet traces are stored in the volume that you specified using the **debug network tcpdump start** command, and can be accessed via the NFS export or an SMB share that corresponds with that volume.

For more information about capturing packet traces, see [ How to use debug network dump in ONTAP 9.10\$1](https://kb.netapp.com/onprem/ontap/hardware/How_to_use_debug_tcpdump_in_ONTAP_9.10) in the NetApp Knowledge Base.